1. Technical Field
The present invention relates generally to an improved data processing system, and in particular to an improved method and apparatus for processing instructions in a data processing system. Still more particularly, the present invention relates to an improved method and apparatus to selectively compile instructions in a data processing system.
2. Description of Related Art
Internet, also referred to as an "internetwork", is a set of computer networks, possibly dissimilar, joined together by means of gateways that handle data transfer and the conversion of messages from the sending network to the protocols used by the receiving network (with packets if necessary). When capitalized, the term "Internet" refer to the collection of networks and gateways that use the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols.
The Internet has become a cultural fixture as a source of both information and entertainment. Many businesses are creating Internet sites as an integral part of their marketing efforts, informing consumers of the products or services offered by the business or providing other information seeking to engender brand loyalty. Many federal, state, and local government agencies are also employing Internet sites for informational purposes, particularly agencies which must interact with virtually all segments of society such as the Internal Revenue Service and secretaries of state. Operating costs may be reduced by providing informational guides and/or searchable databases of public records online.
Currently, the most commonly employed method of transferring data over the Internet is to employ the World Wide Web environment, also called simply "the Web". Other Internet resources exist for transferring information, such as File Transfer Protocol (FTP) and Gopher, but have not achieved the popularity of the Web. In the Web environment, servers and clients effect data transaction using the Hypertext Transfer Protocol (HTTP), a known protocol for handling the transfer of various data files (e.g., text, still graphic images, audio, motion video, etc.). Information is formatted for presentation to a user by a standard page description language, the Hypertext Markup Language (HTML). In addition to basic presentation formatting, HTML allows developers to specify "links" to other Web resources identified by a Uniform Resource Locator (URL). A URL is a special syntax identifier defining a communications path to specific information. Each logical block of information accessible to a client, called a "page" or a "Web page", is identified by a URL. The URL provides a universal, consistent method for finding and accessing this information, not necessarily for you, but mostly for your Web "browser". A browser is a program capable of submitting a request for information identified by a URL at the client machine. Retrieval of information on the Web is generally accomplished with an HTML-compatible browser. The Internet also is widely used to transfer applications to users using browsers.
Users exploring the Web discovered that the content supported by HTML document format on the Web was too limited. Users desired an ability to access applications and programs, but applications were targeted towards specific types of platforms. As a result, not everyone could access applications or programs. This deficiency has been minimized though the introduction and use of programs known as "applets", which may be embedded as objects in HTML documents on the Web. Applets are Java programs that may be transparently downloaded into a browser supporting Java along with HTML pages in which they appear. These Java programs are network and platform independent. Applets run the same way regardless of where they originate or what kind of data processing system onto which they are loaded.
Java is an object oriented programming language and environment focusing on defining data as objects and the methods that may be applied to those objects. Java supports only a single inheritance, meaning that each class can inherit from only one other class at any given time. Java also allows for the creation of totally abstract classes known as interfaces, which allow the defining of methods that may be shared with several classes without regard for how other classes are handling the methods. Java provides a mechanism to distribute software and extends the capabilities of a Web browser because programmers can write an applet once and the applet can be run on any Java enabled machine on the Web. The Java virtual machine (JVM) is a virtual computer component that resides only in memory. The JVM allows Java programs to be executed on a different platform opposed to only the one platform for which the code was compiled. Java programs are compiled for the JVM. In this manner Java is able to support applications for many types of data processing systems, which may contain a variety of central processing units and operating systems architectures. To enable a Java application to execute on different types of data processing systems, a compiler typically generates an architecture-neutral file format of the compiled code that is executable on many processors, given the presence of the Java run time system. The Java compiler generates bytecode instructions that are non-specific to a particular computer architecture. A bytecode is a machine independent code generated by the Java compiler and executed by a Java interpreter. A Java interpreter is a module in the JVM that alternatively decodes and executes a bytecode or bytecodes. These bytecode instructions are designed to be easy to interpret on any machine and easily translated on the fly into native machine code.
Invalid and unpredictable results may sometimes occur from just in time compiling of Java bytecodes. These errors do not occur if the code is not just in time compiled and are typically the results of faulty logic within the just in time compiler. As a result, just in time compiling of applets does not always provide for uniform execution of programs associated with HTML web pages. In addition, the performance of the Java applets of application is not always faster if the application is just in time compiled when the overhead associated with the process of just in time compiling is used for code that is seldom used.
Therefore, it would be advantageous to have an improved method and apparatus for selectively just in time compiling applets in other programs. Traditionally, this problem is addressed by either changing the Java code or recompiling the code to overcome the problems with just in time compiling. In many cases such a fix is not possible or reasonable. Alternatively, the just in time compiler must be serviced and adjusted to avoid the error. Typically, such changes are slow to occur. Alternatively, the just in time compiler can be disabled in the virtual machine, which often times results in performance hits.